An internal combustion engine may emit hydrocarbons, carbon monoxide, and oxides of nitrogen during the course of operation. These emissions may be treated via an after treatment system so that they may be converted to carbon dioxide and water. However, the after treatment system may have to reach an elevated temperature before it begins to convert a high percentage of the engine emissions. If the engine is operated with stoichiometric or lean combustion before the after treatment system reaches operating temperature, tailpipe emissions of hydrocarbons and carbon monoxide may be reduced as compared to if the engine is operated rich. Therefore, an engine may be started and operated with a lean or stoichiometric air-fuel mixture before the after treatment system reaches operating temperature. Nevertheless, it may be difficult at times to get the engine to operate with a stoichiometric or slightly lean air-fuel ratio during engine starting.
The inventors herein have recognized that one potential reason for the engine to not operate with a stoichiometric or lean air-fuel ratio during engine starting and run-up is that small amounts of fuel may be released into engine cylinders or the engine's intake manifold without the fuel injectors being commanded open. The amount of fuel released may be a function of fuel pressure, characteristics of an individual fuel injector, the amount of time the fuel injector is closed and exposed to pressurized fuel, as well as other factors. If fuel is released from a fuel injector while the fuel injector is not being commanded open while an engine is stopped, the released fuel may increase engine hydrocarbon emissions and cause the vehicle to exceed desired emissions levels.
In one example, the issues described above may be addressed by an engine operating method, comprising: identifying a fuel injector of an engine that releases fuel while the fuel injector is commanded off via a controller and a fuel-air ratio indicated from an oxygen sensor during engine cranking and run-up; and adjusting an actuator via the controller based on the fuel injector.
By monitoring output of an oxygen sensor that has reached operating temperature prior to engine cranking and run-up, it may be possible to sense an engine fuel-air ratio Φ so that the technical result of determining the presence or absence of fuel being released from a fuel injector that has not been commanded open may be provided (i.e. injector leak during engine-stopped). In particular, a larger fuel-air ratio during engine starting may indicate that fuel has been released to the engine cylinders after an engine has been stopped. The particular cylinder into which fuel was released via a fuel injector may be determined via starting the engine with a deactivated cylinder and reassessing the engine fuel-air ratio. If the engine fuel air-ratio remains large, a different cylinder may be deactivated for the next engine start and the cylinder that was previously deactivated may be activated during the next start. The process may be repeated until either all cylinders of a cylinder bank have been deactivated once during starting or until the engine fuel-air ratio is reduced. If the engine fuel-air ratio is reduced, the cylinder that was deactivated during the engine start may be identified as the cylinder having a degraded fuel injector.
The present description may provide several advantages. For example, the approach may reduce engine emissions via determining the presence or absence of fuel that may have been released to engine cylinders. Further, the approach may allow for specific cylinder identification so that time to maintain the engine may be reduced. Additionally, the approach may reduce engine fuel consumption.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.